A controversial weed spray has been removed from Auckland Council's gardening practice in select parts of the city as well as on Waiheke.

In 2015, the World Health Organisation said glyphosate, commercially known as Roundup, "probably" has the potential to cause cancer in humans.

Now five of Auckland's 21 local boards will spend funds from their own budget to use mechanical gardening equipment instead.

Mike Cohen is one of the Devonport-Takapuna Local Board members who voted to spend $50,000 to keep his area chemical-free

"We were annoyed with council for using chemical sprays as the default position. We've always had a history of endeavouring to be chemical free," Cohen said.

"A lot of the contractors, I'm not quite sure know the difference between a plant and a weed."

"It's a sort of the dumbing-down effect, where council's trying to get it [work done] cheaper, cheaper and cheaper."

The five local boards which have decided to remain chemical-free are Waiheke, Great Barrier, Devonport-Takapuna, Kaipatiki and Whau.

University of Auckland Associate Professor Malcolm Tingle is a toxicology academic and said glyphosate had the second highest carcinogen rating - Group 2A.

"If it's a probable carcinogen then, realistically, everyone should try and minimise their risk by minimising their exposure," Tingle said.

Speaking about how a commercially available product, like Roundup, would have a 2A carcinogen, Tingle said: "I would have thought it's not that common, particularly if there are alternatives that aren't 2A.

"There are other weed-killers that have a lower classification, although they may not work like glyphosate."

Auckland Council head of operational management Agnes McCormack said council complied with the national Environmental Protection Agency (EPA) rules for use and disposal of glyphosate.

​She said signs were erected to indicate a park was being sprayed.

In August this year, a review commissioned by the EPA conducted by New Zealand scientists, questioned the World Health Organisation's assessment of glyphosate as a "hazard", saying it was "unlikely" to be carcinogenic.

In 2015, Auckland Council introduced a uniform chemical weed-killing practice in 2015, as part of its 10-year-budget, and gave local boards the option of paying for gardening contractors if they did not want glyphosate used.